Hong Kong, July 8 (Reuters): The leader of Hong Kong’s biggest pro-China party said he is considering quitting leader Tung Chee-hwa’s cabinet because huge public opposition to a controversial subversion bill is eroding its popular support.

The defection of a second key ally could be a fatal blow for Tung, who is battling to defuse the biggest political crisis in Hong Kong’s six-year post-colonial era.

Beijing-backed Tung relies on pro-China parties to push through key policies. Tsang Yok-sing, leader of the Beijing-backed Democratic Alliance for the Betterment of Hong Kong, said he was reviewing his role in the cabinet and might walk out.

“I will not rule out quitting the executive council,” Tsang said. “We are looking at all possibilities.” “This (anti-subversion bill) issue is very divisive, contentious and some people are very strongly against it. But since we are in full support of it, those who are against it will not support us (in the coming elections),” he said.

Joseph Cheng, a lecturer on politics at City University, said Tsang’s final decision really hinged on whether Beijing would continue to support Tung.

“Tsang Yok-sing is keeping his options open as Beijing assesses the situation. What Tsang does will be highly indicative of the central government’s support for Tung. If Beijing abandons Tung, of course Tsang will quit the cabinet,” Cheng said.